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Unless you are currently building aerospace product to AS9100 you are probably saying, “What the heck is FOD?” What started out as a requirement to prevent damage to aircraft parts such as engines has been flowed down to any component or assembly including PCBs.
What is FOD?
Foreign object debris/foreign object damage (FOD) is defined by Boeing as, “A substance, debris or article alien to an aircraft or system, which would potentially cause damage.” Foreign object debris can lead to foreign object damage. The classic examples of FOD are things like a wrench or other hand tool left in a jet engine after maintenance has been performed. From a printed circuit board perspective, it means things that can become a permanent part of the product like dirt, dust or other debris that can be entrapped under soldermask or during lamination. It also means surface contamination that could be cleaned off but hasn’t been.
Why is FOD Important?
In an industrial environment, when a part doesn’t work the machine may go down. When something malfunctions in an automobile, the occupants have a high chance of survival. When something malfunctions in a plane, the plane goes down and people die. Aside from the human cost, an airplane is probably one of the most expensive pieces of equipment your product can go into. For example, it can cost more than $1 million to overhaul a McDonnell Douglas MD-80 engine after FOD, $10 million to replace it, with the cost of the entire airplane at around $50 million. A Boeing 747-8 costs in excess of $357 million!
FOD Area Levels FOD programs typically use a three-tier system of controls for activities with different titles in work areas. The system described in this document uses:
1. FOD Awareness Area
2. FOD Sensitive Area
3. FOD Critical Area
To read this entire article, which appeared in the September 2016 issue of The PCB Magazine, click here.